Borinium dyes as sensitizers for organic photoconductors

ABSTRACT

NOVEL METHINE DYES ARE PROVIDED WHICH FEATURE A 1,3,2DIOXABORINIUM SALT MOIETY, 1,3,2 - OXAZABORINIUM SALT MOIETY OR A 1,3,2-DIAZABORINIUM SALT MOIETY. ORGANIC PHOTOCONDUCTORS ARE SPECTRALLY SENSITIZED WITH THE NOVEL DYES OF THIS INVENTION. NOVEL INTERMEDIATES AND METHODS FOR THE PREPARATION OF SUCH INTERMEDIATES ARE ALSO PROVIDED.

United States Patent 3,567,439 BORINIUM DYES AS SENSITIZERS FOR ORGANIC PHOTOCONDUCTORS Daniel S. Daniel and Donald W. Heseltine, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester N.Y. No Drawing. Filed Sept. 23, 1968, Ser. No. 761,860 Int. Cl. G03g 5/08, 13/22 US. Cl. 96-1.6 5 Claims ABSTRACT OF THE DISCLOSURE Novel methine dyes are provided which feature a 1,3,2- dioxaborinium salt moiety, 1,3,2-oxazaborinium salt moiety or a 1,3,2-diazaborinium salt moiety. Organic photoconductors are spectrally sensitized with the novel dyes of this invention. Novel intermediates and methods for the preparation of such intermediates are also provided.

This invention relates to novel dyes and their use in electrophotography.

Elements useful in the electrophotographic process commonly comprise an electrically conductive support bearing a stratum including a photoconductive insulating layer which has a resistivity substantially greater in the dark than in light actinic thereto. Such elements can be used in electrophotographic processes, for example, by first adapting the element in the dark to obtain a uniformly high resistivity in the photoconductive insulating layer, and electrostatically charging the element in the dark to obtain a relatively high potential which may be either negative or positive in polarity. The element can then be exposed to a light pattern which lowers the resistivity and thereby the charge density of the illuminated areas imagewise in proportion to the intensity of illumination incident upon each point of the illuminated areas. A latent electrostatic image is obtained. Visible images can be formed from the latent electrostatic image in any convenient manner, such as by dusting with a finely divided, fusible pigment the particles of which bear an electrostatic charge opposite that remaining on the surface of the photoconductive insulating layer. Thereafter, the pigment particles can be fused to the surface to provide a permanent image.

Various photoconductive substances have been employed in photographic elements and processes of the type described above. Typical inorganic photoconductive materials include selenium and zinc oxide. Such inorganic photoconductive materials have inherent disadvantages, such as an inability to be readily adapted to reflex copying systems, or to produce images on transparent supports except by indirect means. Organic photoconductors avoid such disadvantages, but, generally have relatively poor sensitivity to visible radiation. It has been proposed to increase the spectral sensitivity of organic photoconductors with certain cyanine or rnerocyanine dyes, for example, such as listed in Table D hereinafter. The spectral sensitivity imparted by such dyes has been very weak. It therefore appears highly desirable to provide eifective spectral sensitizers for organic photoconductors.

One object of this invention is to provide novel dyes.

Another object of this invention is to provide novel spectrally sensitized organic photoconductor materials.

Still another object of this invention is to provide novel compositions of matter comprising organic photoconductors and certain spectral sensitizers.

A further object of this invention is to provide novel compositions of matter comprising organic photoconductor, binder and certain spectral sensitizers for the organic photoconductor.

3,567,439 Patented Mar. 2, 1971 Still another object of this invention is to provide a novel electrophotographic material including a conductive support having coated thereon an insulating layer containing spectrally sensitized organic photoconductor.

A further object of this invention is to provide methods for spectrally sensitizing organic photoconductors.

Another object is to provide a novel class of spectral sensitizing dyes and means for preparing these dyes.

Still other objects of this invention will be apparent from the following disclosure and the appended claims.

In accordance with one embodiment of this invention, novel cyanine dyes are provided which contain a moiety selected from the group consisting of a 1,3,2-dioxaborinium salt moiety, a 1,3,2-oxazaborinium salt moiety and a 1,3,2-diazaborinium salt moiety.

In accordance with another embodiment of this invention, novel compositions of matter are provided comprising organic photoconductors spectrally sensitized with the cyanine dyes of this invention. These compositions can be incorporated in a suitable binder and coated on a conductive support for use in electrophotography.

In another embodiment of this invention, compositions of matter are provided comprising organic photoconductors spectrally sensitized with the dyes described herein, dispersed in an insulating binder. These compositions of matter can be coated on a conductive support and used in electrophotographic processes.

In still another embodiment of this invention, electrophotographic materials are provided comprising a conductive support having coated thereon a layer comprising an insulating binder, an organic photoconductor and a spectral sensitizing quantity of a dye defined herein.

In another embodiment of this invention, novel compounds are provided selected from the group consisting of a 1,3,2-dioxaborinium salt; a 1,3,2-oxazaborinium salt and a 1,3,2-diazaborinium salt.

The spectral sensitizing dyes which are employed in this invention, when incorporated in a test negative gelatin silver bromoiodide emulsion consisting of 99.35 mole percent bromide and .65 mole percent iodide, at a concentration of 0.2 millimole of dye per mole of silver halide, desensitize the emulsion more than 0.4 log B when the test emulsion is coated on a support, exposed through a step wedge in a sensitometer (to obtain D to light having a wavelength of 365 nm., processed for three minutes at 20 C. in Kodak Developer Dl9, and is fixed, washed and dried. As used herein and in the appended claims, the test negative silver bromoiodide emulsions are prepared as follows:

In a container with temperature control is put a solution with the following composition:

Potassium bromide: g. Potassium iodide: 5 g. Gelatin: 65 g.

Water: 1700 cc.

And in another container is put a filtered solution consisting of:

Silver nitrate: 200 g. Water: 2000 cc.

Solution A is kept at a temperature of 54 C. during precipitation and ripening, while solution B is put in a separating funnel at a temperature of 54 C. The silver nitrate solution runs from the separating funnel through a calibrated nozzle into the container, the contents of which are kept in constant motion during precipitation and ripening, and later during finishing, by a mechanical stirrer. The precipitation is conducted over a period of 10 minutes.

The developer employed in the test referred to above is Kodak developer D19 which has the following composition:

G. N-Methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrated 52.5 Potassium bromide 5.0

Water to make 1.0 liter.

As indicated above, the dyes employed in this invention desensitize conventional negative silver halide emulsions. Such emulsions are inherently sensitive to blue radiation. The present dyes reduce that sensitivity. In addition, these dyes fail to provide practical spectral sensitization for such emulsions. Therefore, it was quite unexpected to find that they spectrally sensitized organic photoconductors.

The cyanine dyes of this invention increase the speed of organic photoconductors by extending or increasing the response of the photoconductor to visible radiation (i.e., radiation in the range of about 400 nm. to 700 nm.). In the concentrations used, the dyes herein appear to function as spectral sensitizers when employed with efficient organic photoconductors. When the organic photoconductor used is poor or inefiicient, the dyes seem to function as speed increasing compounds as well as spectral sensitizers.

In accordance with this invention, a new class of methine dyes are provided which contain a 1,3,2-dioxa, a 1,3,2-oxazaor a 1,3,2-diazaborinium salt moiety.

Particularly useful methine dyes provided by the invention are styryl dyes which comprise two nuclei joined together by a methine linkage, e.g., a vinyl or butadienyl linkage; the first of said nuclei being a 1,3,2-dioxa-, a. 1,3,2-oxazaor a 1,3,2-diazaborinum salt nucleus, joined at the 4-carbon atom thereof to said linkage; and said second nucleus being a phenyl nucleus joined at a carbon atom thereof to said linkage, to complete said dye.

Other useful methine dyes provided by this invention are simple cyanine and carbocyanine dyes which comprise two nuclei joined together by a methine linkage, e.g., monomethine, trimethine or pentamethine linkage; the first of said nuclei being a l,3,2-dioxa-, a 1,3,2-oxazaor a 1,3,2-diazaborinium salt nucleus, joined at the 4-carbon atom thereof to said linkage; and said second nucleus being a nitrogen containing heterocyclic nucleus of the type used in cyanine dyes having from 5 to 6 atoms in the heterocyclic ring and joined at a carbon atom to said linkage to complete said dye.

Further methine dyes provided by this invention are symmetrical cyanine dyes which comprise two nuclei joined together at the 4-carbon atoms thereof by a methine linkage, e.g., a monomethine, trimethine or pentamethine linkage; said nuclei being selected from the group consisting of a 1,3,2-dioxaborinium salt nucleus, a 1,3,2-oxazaborinum salt nucleus and a 1,3,2-diazaborinium salt nucleus.

Still other useful cyanine dyes provided by this invention are the l-alkyl-2-arylindole type dyes which comprise two nuclei joined together by a methine linkage, e.g., a vinyl linkage; the first of said nuclei being a 1,3,2-dioxa-, a 1,3,2-oxazaor a 1,3,2-diazaborinium salt nucleus joined at the 4-carbon atom thereof to said linkage; and said second nucleus being a 1-alkyl-2-arylindole nucleus joined at the 3-carbon atom thereof to said linkage, to complete said dye.

Other useful cyanine dyes provided by this invention are the pyrazole type dyes which comprise two nuclei joined together by methine linkage, e.g., a vinyl linkage; the first of said nuclei being a 1,3,2-dioxa-, a 1,3,2-oxazaor a 1,3,2-diazaborinium salt nucleus, joined at the 4-carbon atom thereof to said linkage; and said second nucleus being a pyrazole nucleus joined at the 4-carbon atom thereof to said linkage, to com lete said dye.

Typical useful dyes of this invention include those represented by one or more of the following formulas:

wherein d, g, m and 11 each represents a positive integer of from 1 to 2; L represents a methine linkage, e.g., CH=, C(CH C(C H etc., R represents an alkyl group, including substituted alkyl, (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexal, cyclohexyl, decyl, dodecyl, etc., a hydroxyalkyl group, e.g., fl-hydroxyethyl, w-hydroxybutyl, etc., an alkoxyalkyl e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclogroup, e.g., 8-methoxyethyl, w-butoxybutyl, etc., a carboxyalkyl group, e.g., ,B-carboxyethyl, w-carboxybutyl, etc., a sulfoalkyl group, e.g., fl-sulfoethyl, w-sulfobutyl, etc., a sulfatoalkyl group, e.g., B-sulfatoethyl, w-sulfatobutyl, etc., an acyloxyalkyl group, e.g., B-acetoxyethyl, y-acetoxypropyl, w-butyryloxybutyl, etc., an alkoxycarbonylalkyl group, e.g., B-methoxycarbonylethyl, w-ethoxycarbonylbutyl, benzyl, phenethyl, etc.; R represents an aryl group (such as phenyl or naphthyl), a Z-thienyl group or, taken together with R the atoms required to complete a. benzo or naphtho group including substituted nuclei thereof such as chlorobenzo, methylbenzo, nitrobenzo, chloronaphtho, etc.; R taken alone, represents a hydrogen atom; R represents a dialkylamino group (preferably those wherein each alkyl is a lower alkyl containing from 1 to 4 carbon atoms), e.g., dimethylamino, dibutylamino, etc., an alkoxy group (preferably a lower alkoxy containing from 1 to 4 carbon atoms), e.g., methoxy, butoxy, etc., a styryl group, or a nitro group, etc.; R represents an aryl group, e.g., phenyl, tolyl, chlorophenyl, methoxyphenyl, nitrophenyl naphthyl, etc.; R represents an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, propyl, isopropyl, butyl, decyl, etc.; R represents an aryl group, e.g., phenyl, tolyl, methoxyphenyl, chlorophenyl, nitrophenyl, naphthyl, etc.; R and R each represents an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, isopropyl, butyl, decyl, etc.; X represents an acid anion, e.g., chloride, bromide, iodide, fluoride, thiocyanate, sulfamate, perchlorate, p-toluenesulfonate, methyl sulfate, etc.; D and D each represents an oxygen atom or an imino group, such as an imino group of the formula N(R), wherein R represents hydrogen or aryl, e.g., imino, e.g., methylimino, butylimino, etc., or an arylimino, e.g., phenylimino, tolylimino, naphthylimino, etc., D; being an imino group when D represents an imino group; and Z represents the non-metallic atoms required to complete a heterocyclic nucleus containing from 5 to 6 atoms in the heterocyclic ring, which nucleus may contain a second hetero atom such as oxygen, sulfur, selenium or nitrogen, such as used in cyanine dyes, and including the following nuclei: a thiazole nucleus, e.g., thiazole, 4- methylthiazole, 4 phenylthiazole, 5 methylthiazole, 5- phenylthiazole, 4,5-dimethylthiazole, 4,5-diphenylthiazole, 4-(2-thienyl)thiazole, benzothiazole, 4 chlorobenzothiazole, 4-chloro-5 nitrobenzothiazole, 5 chlorobenzothiazole, 6 chlorobenzothiazole, 7 chlorobenzothiazole, 4- methylbenzothiazole, 5 methylbenzothiazole, 6 methylbenzothiazole, 4- or S-nitrobenzothiazole, 6-nitrobenzothiazole, S-bromobenzothiazole, 6-bromobenzothiazole, 5- chloro 6 nitrobenzothiazole, 4-phenylbenzothiazole, 4- methoxybenzothiazole, 5 methoxybenzothiazole, 6 methoxybenzothiazole, S-iodobenzothiazole, 6-iodobenzothia'zole, 4-ethoxybenzothiazole, S-ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6 dimethoxybenzothiazole, 5,6- dioxymethylenebenzothiazole, S-hydroxybenzothiazole, 6- hydroxybenzothiazole, naphtho[2,1-d]thiazole, naphtho- 1,2-d] thiazole, naphtho 2,3-d] thiazole, S-methoxynaphtho[2,3-d]thiazole, 5 -ethoxynaphtho[1,2-d]thiazole, 8- methoxynaphtho[2,1 d]thiazole, 7 methoxynaphtho- [2,1-d] thiazole, 5 -methoxythianaphtheno- [7 ,6-d] thiazole, nitro substituted naphthothiazoles, etc.; an oxazole nucleus, e.g., 4-methyloxazole, 4-nitrooxazole, S-methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole, S-phenyloxazole, benzoxazole, S-methylbenzoxazole, S-phenylbenzoxazole, 5- or 6-nitrobenzoxazole, S-chloro-6-nitrobenzoxazole, 6-methylbenzoxazole, 5,6-dimethy1benzoxazole, 4,6 dimethylbenzoxazole, S-methoxybenzoxazole, S-ethoxybenzoxazole, S-chlorobenzoxazole, 6-methoxybenzoxazole, S-hydroxybenzoxazole, 6 hydroxybenzoxazole, naphtho[2,1 d]oxazole,

naphtho[1,2-d] oXazole, nitro substituted naphthoxazoles,

etc.; a selenazole nucleus, e.g., 4-methylselenazole, 4- nitroselenazole, 4-phenylselenazole, benzoselenazole, 5- chlorobenzoselenazole, 5-methoxybenzoselenazole, S-hydroxybenzoselenazole, 5- or 6-nitrobenzoselenazole, 5- chloro-6-nitrobenzoselenazole, tetrahydrobenzoselenazole, naphtho [2,1-d] selenazole, naphtho[1,2-d]selenazole, nitro substituted naphthoselenazoles, etc.; a thiazoline nucleus, e.g., thiazoline, 4-methylthiazoline, 4-nitrothiazoline, etc.; a pyridine nucleus, e.g., 2-pyridine, 5-methyl-2-pyridine, 4-pyridine, 3-methyl-4-pyridine, nitro substituted pyridines, etc.; a quinoline nucleus, e.g., 2-quinoline, 3-methyl- 2-quinoline, S-ethyl-Z-quinoline, 6-chloro-2-quinoline, 6- nitro-2-quinoline, 8-chloro-2-quinoline, 6-methoxy-2-quinoline, 8-ethoxy-2-quinoline, 8-hydroxy-2-quinoline, 4-quinoline, 6-methoxy-4-quinoline, 6 nitro 4 quinoline, 7- methyl-4-quinoline, 8-chloro-4-quinoline, l-isoquinoline, 6-nitro-1-isoquinoline, 3,4-dihydro-l-isoquinoline, 3-isoquinoline, etc.; a 3,3-dialkylindolenine nucleus, preferably having a nitro or cyano substituent, e.g., 3,3-dimethyl- 5- or 6-nitroindolenine, 3,3-dimethyl-5- or 6-cyanoindolenine, etc.; and, an imidazole nucleus, e.g., imidazole, 1- alkylimidazole, l-alkyl-4-phenylimidazole, 1-alky1-4,5 dimethylimidazole, benzimidazole, l-alkylbenzimidazole, 1- aryl-5,6-dichlorobenzimidazole, l-alkyl-lH naph[l,2-d]- imidazole, 1-aryl-3H-naphth[1,2-d]irnidazole, 1-alkyl-5- methoxy-lH-naphth[2,1-d]imidazole, etc.; an imidazo- [4,5-d]quinoxaline nucleus, e.g., a 1,3-dialkylimidazo- [4,5-b]quinoxaline such as 1,3-diethylimidazo [4,5-b]quinoxaline, 6-chloro 1,3 diethylimidazo[4,5-b]quinoxaline, etc., a 1,3-dialkenylimidazo[4,5-b]quinoxaline such as 1,3-diallylimidazo [4,5-b] quinoxaline, 6-chloro-1,3-diallylimidazo[4,5-b1quinoxaline, etc., a 1,3 diarylimidazo- [4,5-b]quinoxaline such as 1,3-diphenylimidazo[4,5-b]- quinoxaline, 6-chloro-1,3 diphenylimidazo [4,5-b]quinoxaline, etc.; a 3,3-dialkyl-3H-pyrrolo[2,3-b] pyridine nucleus, e.g., 3,3-dirnethyl-3H-pyrrolo[2,3-b]pyridine, 3,3- diethyl-SH-pyrrolo[2,3-b] pyridine, etc.; a thiazolo [4,5-b]- quinoline nucleus; and the like. The nuclei wherein Z in above Formula II represents the atoms necessary to complete an electron-accepting nucleus such as a nitro substituted thiazole, oxazole, selenazole, thiazoline, pyridine, quinoline, 3,3-dialkylindolenine or imidazole nucleus; or an imidazo[4,5-b]quinoxaline, 3,3-dialkyl 3H pyrrolo- [2,3-b]pyridine or thiazolo[4,5-b]quinoline nucleus; and the like; provide useful spectral sensitizing dyes for the photoconductor compositions and elements of this invention. The styryl type dyes of the invention defined by Formula I above are especially efiicacious sensitizers and are the preferred dyes of this invention.

As used herein and in the appended claims, electron accepting nucleus refers to those nuclei which, then converted to a symmetrical carbocyanine dye and added to a gelatin silver chlorobromide emulsion containing 40 mole percent chloride and 60 mole percent bromide, at a concentration of from 0.01 to 0.2 grams dye per mole of silver, cause by electron trapping at least about an percent loss in the blue speed of the emulsion when sensitometrically exposed and developed three minutes in Kodak developer D-19 at 20 C., the composition of which is given above. Preferably, the electron-accepting nuclei are those which, when converted to a symmetrical carbocyanine dye and tested as just described above, essentially completely desensitize the test emulsion to blue radiation. Substantially complete desensitization as used herein, results in at least a percent, and preferably a percent loss of speed to blue radiation.

The cyanine dyes of Formula I above are conveniently prepared, for example, by heating a mixture of (l) a heterocyclic compound of the formula:

VI. R2 Ills 69D CCH3 X and (2) an aldehyde of the formula:

VII.

VIII.

wherein n, R X and Z are as previously defined; k represents 0 or 1; and, W represents the group SR wherein R is an alkyl or aryl group, e.g., methyl, phenyl etc. for the preparation of the simple cyanine dyes of the 70 invention, or W represents the group pounds of Formulas VI and VIII above, in the presence of alweakly basic condensing agent such as pyridine, 2,6- lutidine, etc. in a solvent medium such as acetic anhydride. The dyes are then separated from the reaction mixtubs and purified by one orgnore recrystallizations from appropriate solvents such as acetonitrile.

.For the preparation of the symmetrical cyanine dyes of this invention defined by Formula III above, a mixture comprising (1) a compound of Formula VI above and (2) a compound such as a dialkoxymethylacetate, e.g., diethoxymethylacetate, or a trialkoxypropene,-e.g., trirnethoxypropene, etc., is reacted by heating to boiling in the presence of a weakly basic condensing agent, e.g., 2,6-lutidine, in a solvent medium such as acetic anhydride in the proportions of about 2 moles of (l) and at least 1 mole of (2) the crude dyes obtained are purified by one or more recrystallizations from appropriate solvents such as acetonitrile.

The cyanine dyes defined by Formulas IV and V above are conveniently prepared by heating a mixture comprising (1) a compound of Formula VI above and (2) a compound selected from (a) a compound of the formula:

or (b) a compound of the formula:

wherein R is a suitably substituted aryl e.g., Z-aminophenyl, 2-hydroxyphenyl, 2-hydroXy-a-naphthyl, etc. or an acyl substituted methyl e.g., acetylmethyl, CH COCH 2-thienoylmethyl, etc. or a precursor which can be converted to the latter in the presence of (2) and acetic anhydride, for example 6(2-thienyl)-4-methyl-1,3,2-dioxaborinium fluoride from Z-thienyl-methyl ketone, with (2) boron-tritiuoride ethyl ether complex to give the corresponding 1,3,2-dioxaborinium or the 1,3,2-oxazab0rinium salts. By treatment with an arylamine, e.g., aniline, the above salts are converted to the 3-arylimido substituted 1,3,2-oxazaborinium and 3-arylimido substituted 1,3,2-diazaborinium salts, respectively.

Dyes such as illustrated above can be used alone, or a combination of one or more of the above described dyes can be used to impart the desired spectral sensitivity. All of them are spectral sensitizers for organic photoconductors. Suitable organic photoconductors which are effectively spectrally sensitized by such dyes include both monomeric and polymeric organic photoconductors. The invention is particularly useful in increasing the speed of organic photoconductors which are substantially insensitive, or which have low sensitivity (e.g., a speed less than 8 25 but generally less than 10 when tested as described in Examples 1 to 6 below) to radiation of 400 to 700 nm;

An especially useful class of organic photoconductors is referred to herein as organic amine photoconductors. Such organic photoconductors have as a common structural feature at least one amino group. Useful organic photoconductors which can be spectrally sensitized in accordance with this invention include, therefore, arylamine compounds comprising (1) diarylamines such as diphenylamine, dinaphthylamine, N,N'-diphenylbenzi-:line, N-phenyl 1 naphthylamine; N-phenyl-Z-naphthylamine; N,N-diphenyl-p=phenylenediamine; 2 carboxy-S-chloro- 4'-methoxydiphenylamine; p-anilinophenol; N,N' di 2- naphthyl-p-phenylene diamine; 4,4-benzylidene-bis(N,N- diethyl-m-toluidine), those described in Fox US. Pat. 3,240,597 issued Mar. 15, 1966, and the like, and (2) triarylamines including (a) nonpolymeric triarylamines, such as triphenylamine, N,N,N',N'-tetraphenyl-m-phenyl enediamine; 4-acetyltriphenylamine, 4-hexanoyltriphenylamine; 4-lauroyltriphenylamine; 4 hexyltriphenylamine, 4-dodecyltriphenylamine, 4,4-bis diphenylamino -benzil, 4,4 bis(diphenylamino) benzophenone, and the like, and (b) polymeric triarylamines such as poly[N,4"- (N,N,N'-triphenylbenzidine) polyadipyltriphenylamine, polysebacyltriphenylamine; polydecamethylentriphenylamine; poly N (4-vinylphenyl)-diphenylamine, poly-N- (vinylphenyl)-a,a-dinaphthylamine and the like. Other useful amine-type photoconductors are disclosed in US. Pat. 3,180,730, issued Apr. 27, 1965.

Other very useful photoconductive substances capable of being spectrally sensitized in accordance with this invention are disclosed in Fox US. Pat. 3,265,496 issued Aug. 9, 1966, and include those represented by the following general formula:

wherein A represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear, (e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, ethoxy, propoxy, pentoxy, etc.), or a nitro group; A represents a mononuclear or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc); or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from 1 to about 6 carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from 1 to about 6 carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from 1 to about 6 carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.), or a nitro group; Q can represent a hydrogen atom, a halogen atom or an aromatic amino group, such as ANI-I; b represents an integer from 1 to about 12, and G represents a hydrogen atom, a mononuclear or polynuclear aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly (4'-vinylphenyl) group which is bonded to the nitrogen atom by a carbon atom of the phenyl group. Certain nitrogen heterocyclic compounds are also useful photoconductors in the invention such as, for example, 1,3,5-triphenyl-2- pyrazoline, 2,3,4,5-tetraphenylpyrrole, etc.

Polyarylalkane photoconductors are particularly useful in producing the present invention. Such photoconductors are described in US. Pat. 3,274,000; French Pat. 1,383; 461 and in a copending application of Seus et al. Ser. No. 624,233, Photoconductive Elements Containing Organic 9 Photoconductors filed Mar. 20, 1967. These photoconductors include leuco bases of diaryl or triaryl methane dye salts, 1,1,1-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes, there being substituted an amine group on at least one of the aryl groups attached to the alkane and methane moieties of the latter two classes of photoconductors which are non-leuco base materials.

Preferred polyaryl alkane photoconductors can be represented by the formula:

wherein each of D, E and G is an aryl group and J is a hydrogen atom, an alkyl group, or an aryl group, at least one of D, E and G containing an amino substituent. The aryl groups attached to the central carbon atom are preferably phenyl groups, although naphthyl groups can also be used. Such aryl groups can contain such substituents as alkyl and alkoxy typically having 1 to 8 carbon atoms, hydroxy, halogen etc. in the ortho, meta or para positions, ortho-substituted phenyl being preferred. The aryl groups can also be joined together or cyclized to form a fluorene moiety, for example. The amino substituent can be represented by the formula wherein each R can be an alkyl group typically having 1 to 8 carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having 5 to 6 atoms in the ring such as morpholino, pyridyl, pyrryl, etc. At least one of D, E and G is preferably p-dialkylaminophenyl group. When I is an alkyl group, such an alkyl group more generally has 1 to 7 carbon atoms.

Representative useful polyarylalkane photoconductors include the compounds listed below:

TABLE A Compound No.:

(1) 4,4-bis-(diethylamino)-2,2-d1methyltriphenyl methane.

phenylmethane. (11) 4,4-bis (benzylethylamino)-2,2-dimethyltriphenylmetha e (12) 4,4'-bis(diethylamino)-2,2-diethoxytriphenylmethane.

4,4-bis (dimethylarm'no)-1,1,1-triphenylethane.

(14) 1-(4-N,N-diemthylaminophenyl)-1,1-diphenylethane.

(15) 4-dimethylaminotetraphenylmethane.

(16) 4-diethylaminotetraphenylmethane.

As described herein a wide variety of photoconductor compounds can be spectrally sensitized with the dyes referred to above. Some organic photoconductors will, of course, be preferred to others; but in general useful results may be obtained from substantially all of the presently known organic photoconductors.

The following Table B comprises a partial listing of US. patents describing such organic photoconductors and compositions which can be used in place of those more particularly described herein.

TABLE B Patent; Inventor Issued N umbels Noe et al February 25, 1964 3,122,435 Sus et al March 31, 1964 3,127, 266 Schlesinger. April 21, 1964 3,130, 046 Cassiers. April 28, 1964 3, 131, 060 Schlesinger June 30, 1964. 3, 139, 338 Schlesinger. June 30, 1964 3, 139, 339 Cassiers. July 14, 1964-- 3, 140, 946 3, 141, 770 3, 148, 982 3,155, 503 3,158,475 3, 161, 505 3,163,530 1,163,531 3,163,532 3,169,060 March 23, 1965 3,174,854 April 27, 1965- 3,180,729 Kluptel et al 3, 180, 730 Neugebauer 3, 189, 447 N eugebauer- 3, 206, 306 Davis et al 3,151,770 Hoegl et al 3, 037, 861 Sus et al 3, 041, Schlesinger 3, 066, 023 ethe 3, 072, 479 Klupfel et al. 3, 04:7, 095 Neugebauer et a1- 3, 112, 197 Gassiers et a1 3,113,022 Schlesinger. 3, 114, 633 Kosehe et a1 3, 265, 497 Noe et al 3, 274, 000

The spectrally sensitized organic photoconductor compositions of this invention can, in certain arrangements, be employed in electrophotographic elements in the absence of binder. For example, the photoconductor itself is sometimes capable of film formation, and therefore requires no separate binder. An example of such filmforming photoconductor is poly(vinylcarbazole). However, the more common arrangement is to provide a binder for the spectrally sensitized organic photoconductive materials. Any suitable binder material can be utilized for the spectrally sensitized organic photoconductors of the invention. Such binders should possess high dielectric strength, and have good insulating properties (at least in the absence of actinic radiation) as well as good film forming properties. Preferred binder materials are polymers such as polystyrene, poly(methylstyrene), styrenebutadiene polymers, poly(vinyl chloride), poly(vinylidene chloride), poly(vinylacetate), vinyl acetate-vinyl chloride polymers, poly(vinylacetals), polyacrylic and methacrylic acid esters, polyesters such as poly (ethylene al-karyloxy-alkylene terephthalates), phenol-- fomaldehyde resins, polyamides, polycarbonates and the like.

The photoconductive compositions of the invention can be coated on any of the electrically conductive supports conventionally used in electrophotographic processes, such as metal plates or foils, metal foils laminated to paper or plastic films, electrically conductive papers and films, papers and films coated with transparent electrically conductive resins and the like. Other useful conducting layers include thin layers of nickel coated by high vacuum deposition and cuprous iodide layers as described in US. Patent 3,245,833. Transparent, translucent or opaque support material can be used. Exposure by reflex requires that the support transmit light while no such requirement is necessary for exposures by projection. Similarly transparent supports are desired if the reproduction is to be used for projection purposes; translucent supports are preferred for reflex prints; and opaque supports are adequate if the image is subsequently transferred by any means to another support, the reproduction is satisfactory as obtained, or the reproduction is to be used as a printing plate for preparing multiple copies of the original.

The quantity of the above-described dye required to spectrally sensitize an organic photoconductor varies with the results desired, the particular dye used, and the particular organic photoconductor used. Best results are obtained with about .01 to 10 parts by weight dye and 1 1 about 1 to 75 parts by weight of the organic photoconductor based on the photoconductive composition. Binder can be employed in such compositions, when desired, at preferred ranges of 25 to 99 parts by Weight. In addition, the composition can contain other sensitizers, either spectral sensitizers or speed increasing compounds, or both.

As used herein and in the appended claims, the terms insulating and electrically conductive have reference to materials the surface resistivities of which are greater than ohms per square unit (e.g., per square foot) and less than 10 ohms per square unit (e.g., per square foot) respectively.

Coating thicknesses of the photoconductive compositions of the invention on a support can vary Widely. As a general guide, a dry coating in the range from about 1 to 200 microns is useful for the invention. The preferred range of dry coating thickness is in the range from about 3 to 50 microns.

To produce a reproduction of an image utilizing the electrophotographic elements of our invention, the photoconductive layer is preferably dark adapted, and then is charged either negatively or positively by means of, for example, a corona discharge device maintained at a potential of from 6000-7000 volts. The charged element is then exposed to light through a master, or by reflex in contact with a master, to obtain an electrostatic image corresponding to the master. This invisible image may then be rendered visible by being developed by contact with a developer including a carrier and toner. The carrier can be, for example, small glass or plastic balls, or iron powder. The toner can be, for example, a pigmentedthermoplastic resin having a grain size of from about 1-100 which may be fused to render the image permanent. Alternatively, the developer may contain a pigment or pigmented resin suspended in an insulating liquid which optionally may contain a resin in solution. If the polarity of the charge on the toner particles is opposite to that of the electrostatic latent image on the photoconductive element, a reproduction corresponding to the original is obtained. If, however, the polarity of the toner charge is the same as that of the electrostatic latent image, a reversal or negative of the original is obtained.

Although the development techniques described hereinabove produce a visible image directly on the electro-' photographic element, it is also possible to transfer either the electrostatic latent image, or the developed image to a second support which may then be processed to obtain the final print. All of these development techniques are well known in the art and have been described in a number of US. and foreign patents.

The following examples are included for a further understanding of this invention.

EXAMPLE 1 4- 4-dimethylamin0styryl -2-fluoro-benzo [e] 1,3,2-dioxaborinium fluoride A mixture of 2-fluoro-4-methyl-1,3,2-benzo[e]dioxaborinium fluoride (1.84 g.), p-dimethylaminobenzaldehyde (1.51 g.) and acetic anhydride mls.) is heated under reflux for ten minutes and allowed to cool; the dye is collected on a filter and Washed with ethyl acetate. The yield is 2.42 g. (77%). After recrystallization from acetonitrile, the green crystals melt at 256257 C., with decomposition.

By substituting an equivalent amount of o her intermediate aldehydes embraced by Formulas VII, IX and X in place of the pdimethylaminobenzaldehyde in the procedure of above Example 1, the corresponding cyanine dyes of the invention are readily obtained. Typical dyes prepared in this manner include 4-(4-dimethylaminostyryl)-2-fluoro-3-phenyl-benzo [e] [1,3,2] -oxazaborinium salt (e.g., the chloride, bromide, iodide, fluoride, perchlorate, p-toluenesulfonate, etc. salts).

CH=CH-N l Ii -Cells or 4- 4-dimethylaminostyryl -2-fluoro-3 -phenyl-benzo [e] [1,3,2]-diazaborinium salt (e.g., the chloride, bromide, iodide, fluoride, perchlorate, p-toluenesulfonate, etc.

and the like dyes.

Still other dyes that are readily prepared in accordance with the general procedure of above Example 1 include the following typical dye examples, the yields and melting points being listed in Table l.

TABLE 1 Percent Melting yield point, C.

Compound:

EXAMPLE 2 2,2-difluoro-4,4- (benzo [e] -l,3,2-dioxaborino) carbocyanine fluoride A mixture of 2-fluoro-4-methyl-benzo[e]-1,3,2-dioxaborinium fluoride (3.68 g.) and acetic anhydride (20 mls.) is heated until solution is complete. Diethoxymeth ylacetate (1.61 g.) is added and the mixture heated to boiling. 2,6-lutidine (2 mls.) is added and the mixture heated under reflux for 3 minutes. The mixture is allowed to cool and is then poured over ether (400 mls.). The dye is collected on a filter and washed with ether. The yield is 0.74 g. (20%). After recrystallization from acetonitrile, the dark crystals melt at 183-184 C., with decomposition.

(B) 2,2'-difluoro 4,4 naphtho[1,2 d] 1,3,2-dioxaborinocarbocyanine fluoride is prepared similarly. The yield is 14%. The dark crystals melt at 203-204 C., with decomposition.

EXAMPLE 3 -2,2'-difluoro-4,4'-naphtho[ 1,2-d] -1,3,2- dioxaborinodicarbocyanine fluoride A mixture of 2-fluoro-4-methylnaphtho[1,2-d]-1,3,2-dioxaborinium fluoride (2.34 g.), trimethoxypropane (0.66 g.) and acetic anhydride (20 mls.) is heated to boiling and 2,6-lutidine (2 mls.) added. The mixture is heated under reflux for 3 minutes; it is allowed to cool and poured over ether (400 mls.). The dye is collected on a filter and washed with ether. The yield is 1.10 g. (45% After recrystallization from acetonitrile, the dark crystals did not melt below 300 C.

(B) 2,2 difluoro 4,4-(benzo[e]-1,3,2-dioxaborino)- dicarbocyanine fluoride is prepared similarly. The yield after recrystallization from acetonitrile is 4%. The dark crystals melt at 151'152 C., with decomposition.

EXAMPLE 4 3'-ethyl-2-fluoro-4-(benzo[e]-1,3,2-dioxaborino)-2.-thiacyanine iodide A mixture of 2-fluoro-4-methyl-benzo[e]-1,3,2-dioxaborinium fluoride (1.84 g.), Z-phenylthio-3-ethylbenzothiazolium iodide (3.99 g.) and acetic anhydride (15 mls.) is heated until solution is complete; 2,6-lutidine (1 ml.) is added. The mixture is heated under reflux for 3 minutes and allowed to cool and then poured over ether. The yield is '1.27 g. (26% After recrystallization from acetonitrile, the reddish crystals melt at 253-254 C.

EXAMPLE 2-flu0ro-1',3',3'-trimethyl-4-(benzo [e]-1,3,2- dioxoborino) -2'-indocarbocyanine iodide complete; pyridine (2 mls.) is added and the mixture is heated under reflux for 3 minutes. The mixture is allowed to cool and then poured over ether (400 mls.). The ether is decanted and the dye washed with ether. After recrystallization from acetonitrile the yield of dye is 0.16 g. (3%). The dark crystals melt at 222223 C. with decomposition.

In the place of the 2 B acetanilidovinyl 1,3,3 trimethyl 3H indolium iodide in the above example, there is substituted an equivalent amount of any other of the intermediates coming under Formula VIII above to give the corresponding carbocyanine dyes. Typical dyes prepared in this manner include such as the following.

(A) 3' ethyl 2 fluoro 4 naphtho [l,2-d]-1,3,2-

dioxaborino-Z'-oxacarbocyanine iodide (B) 3 ethyl 2 fluoro 4 naphtho [1,2-d]-l,3,2-dioxaborino-2'-thiacarbocyanine iodide (C) 1' ethyl 2 fluoro 4 naphtho [1,2-d]-1,3,2-

dioxaborino-2'-carbocyanine iodide TABLE 2 Percent Melting yield point, 0.

Compound:

A 35 300 B 3 210-212 C l 5 224-226 1 After recrystallization.

It will be apparent from the foregoing that the procedure of above Example 5 can also be advantageously used to prepare still other cyanine dyes of the invention embraced by Formula II above, for example, 3 methyl- 2 fluoro 4 (benzo[e] 1,3,2 dioxaborino)-2-selenacarbocyanine salt (e.g., the chloride, bromide, iodide, fluoride, perchlorate, p-toluenesulfonate, etc. salts) by replacing the 2. [3 acetanilidovinyl 1,3,3 trimethyl- 3H indolium iodide with an equivalent amount of 2-5- acetanilidovinyl 1 methylbenzoselenazolium salt.

EXAMPLE 6 4- (4-dimethylaminostyryl) -2-fluoro-6-pheny1- 1,3,2-dioxaborinium fluoride A mixture of 2 fluoro 4 methyl 6 phenyl 1,3,2- dioxaborinium fluoride (1.05 g.), p-dimethylaminobenzaldehyde (0.80 g.) and acetic anhydride (10 ml.) is heated under reflux for five minutes and allowed to cool; the dye is collected on a filter and washed with ether. The yield is 1.20 -g. After recrystallization from acetonitrile, the crystals melt at 231232 C.

EXAMPLE 7 2-fluoro-4- [2- l-methyl-2-phenyl-3 -indolyl) vinyl] 6- (4-nitrophenyl) 1,3 ,2-dioxaborinium fluoride r 9 F F CHs A mixture of 2 fluoro 4 methyl -6 (4 -nitrophenyl) 1,3,2 dioxaborinium fluoride (1.04 g.), 1- methyl 2-phenyl-3-indolcarboxaldehyde (0.80 g.) and acetic anhydride (10 ml.) is heated under reflux for five minutes and allowed to cool; the dye is collected on a filter and washed with ether. The yield of dye is 1.10 g. (57% After recrystallization from acetonitrile, the crystals melt at 266-26-8 C.

aniline (18.6 g.) is added and the mixture is heated ung g i der reflux with a water take-off for two hours. The mixfl 1d YD- A i ture is allowed to cool when the product separates as a diXQa 01'in0)-Car CY flufiridfi White solid. It is collected on the filter and Washed with h r ether. The yield is 22.5 g. (81%). After recrystallization from acetonitrile, the whie crystals melt at 175176 C.,

m m-on=on-on=m m j with decomposition.

In place of the 2-fluoro-A-methyi-1,3,2-be zodioxai bor inium fluoride in the above example, there is substih g 9 V 10 tuted other appropriate borinium saltsto give the follow- F F 1: ing typical compounds. 7 h A mixture of 2 fiuoro 4 methyl 6 (2 thienyl)- (A) i -Li a 1,3,2 dioxaborinium fluoride (2.16 g.), diethoxymethylborlmum fluonde i acetate (0.81 g.) and butyrolactone (10' ml.) is heated (B) P' f to boiling and 2,6-lutidine 1 ml.) added. The mixture is v Oxazabormwm fluorlde heated under reflux for three minutes; it is allowed to cool, filtered and washed with ether. The yield of dye is F i TABLE 4 0.82 g. (31%). After recrystallization from acetonitrile Percent Melting the crystals melt at 197-199 C. yield point, C.

To prepare the novel l,3,2-dioxa(or oxaza or diaza) Compound.

'borinium salt intermediates of the invention defined by A 72' 198-199 Formula VI above, a number of variations in method B 78 268-269 are required. These are illustrated by the following eX- 7 if amples' him 7 EXAMPLE 11 j E 2-fluoro-4-methyl-benzo [d] -1,3,2-oxazaborinium fluoride 2-fluoro-4-methy1-benzo [e] .-1 ,3,2-dioxaborinum flllOIidC CH3 T K /\0@ e 2; V F t f 7 iii B F I N \O V H e Fe V 2 hydroxyacetophenone (6.8 g.) is slowly added to Z-aminoacetophenone (4.5 g.) is slowly added to chilled, chilled, stiired borontrifluoride ethyl ether complex (20 stirred boron trifiuoride ethyl ether complex (25 mls.). mls.). The product, which precipitates immediately, is The mixture is stirred at room temperature for 15 minutes.

collected on the filter and washed with ether. The yield The yellow product is collected on a filter and washed is 5.6 g. (62%). The yellow crystals melt at 146-147 40 with ether. The yield is 5.9 g. (92%). The pale yellow .C with decomposfiond h h b crystal smelt at 161-165 "C., with idecomposition. By replacing the 2 hy roxyacetop enone in t e a ove I 'example with other appropriate hydroxy substituted aryl- '7 EXAMPLE 12 methylketones, a 1,3-diketone, the following other in- 2-flucfro-4-methyl-l-phenyl-benzoie]-1,3,2-diazaboriu m termediates are prepared. fluoride I I (A) 2 fluoro 4 methyl 6 7 phenyl 1,3,2 dioxaboriniurn fluoride *1 CHa (B) 2 fluoro-benzo[e]-1,3,2-dioxaboriniurn fluoride l (C) 2-fluoro-naphtho[1,2-d]-1,3.2-dioxaborinium flue-ride I Q F (D) 2-fuoro-7,8-dihydroXy-4-methyl-benzo[e]- BQ-F 1,3,2-dioxaborinium fluoride g dioxaborinium fluoride L i W TABLE 3 5 To a suspension of 2-fiuoro-3-hydro-4-methyl-benzo- 7 N [d] 1,3,2-oxazab-orinium fluoride (3.7 g.) in benzene 332 5 g g g V (100 ml.) aniline (4.0 g.) is added and the mixture is V heated under reflux for two hours with a water take-off.

7 X 72 156457 The mixture is allowed to cool and the product collected 6 on the filter and washed with ligroin. The yield is 3.1 g. 3% 'i-a' g (61%). The pale yellow crystals melt at a temperature 96 V 240-24l pver 300? C. with decomposition. W

7 EXAMPLE 1e 7 W 13 2 fluoro 4;methy1 3. phenyl l5enzo [e1 1,32 6 5 2-fiuoro-4-methyl-6-phenyl-1 ,3,2- d1oxabonn1um fluoride V oxzaborinium fluoride (3H3 g V f can. Fem e e I N LCGH i5 10 n /V: e W O// l F F e e 7 W 7 7 7 To asuspension of2-fluoro =4-methyl-benzo[e]-1,3,2- To a solution of benzoylacetone (32.4 g.) in ether dioxaborinium fluoride (18.4 g.) in benzene (150 mls.) (ISQ ml.), there is added boron trifluoride ethyl ether 1 7 complex (150 ml.). The mixture is stirred for one hour. The precipitated compound is then filtered off and washed with ether. The yield is 30 g. (72%), M.P. 156157 C.

EXAMP-LE 14 2-fluoro-4-methyl-6-(Z-thienyl) -1,3,2- dioxaborinium fluoride A mixture of Z-thienylmethylketone (42 g.), borontrifluoride ethyl ether complex (110 ml.) and acetic anhydride (107 g.) is stirred for 15 minutes and then warmed at 55 C. for 30 minutes. The mixture is suspended in water and stirred two hours at room temperat-ure, filtered and the collected product is washed. The yield is 17 g. (24%). The grayish powder melts at 170- 172 C.

EXAMPLE 15 2-fluoro-4-methyl-6- (4-nitrophenyl) -1,3 ,2- dioxaborinium fluoride The procedure of above Example 14 is repeated, except that the Z-thienylmethylketone is replaced With p-nitroacetophenone (55 g.). The yield of compound is 20 g. (24%), M.P. 188-189 C. Y

The dyes of the invention prepared in accordance with the preceding examples markedly increase the speed of organic photoconductors when added thereto. This increase in speed is due to the spectral sensitivity imparted to the photoconductor by the dyes described herein. The evaluations set forth in Table 5 below show greatly increased speeds with maximum sensitivity peaks (Abs max.) extending to radiation in the region of the spectrum of from about 500 to 600 nm. The method of evaluation is as follows:

A series of solutions are prepared consisting of 5.0 ml. methylene chloride (solvent); 0.15 g. 4,4 bis(diethylamino)-2,2'-dimethyltriphenylmethane (organic photoconductor); 0.50 g. polyester composed of terephthalic acid and a glycol mixture comprising a 9:1 weight ratio of 2,2 bis [4 (2 hydroxyethoxy)-phenyl] propane and ethylene glycol (binder) and 0.0065 g. of the spectral sensitizing dye indicated by identifying number from above Table A. Each solution is coated on an aluminum surface maintained at 25 C., and dried. All operations are carried out in a darkened room. A sample of each coating is uniformly charged by means of a corona to a potential of about 600 volts and exposed through a transparent member bearing a pattern of varying optical density to a 3000 K. tungsten source. The resultant electrostatic image pattern is then rendered visible by cascading a developer composition comprising finely divided colored thermoplastic electrostatically responsive toner particles carried on glass beads over the surface of the element. The image is then developed by deposition of the toner in an imagewise manner on the element. (Other development techniques such as those described in US. 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,874,063;

2,984,163; 3,040,704; 3,117,884; Re. 25,779; 2,297,691; 2,551,582; and in RCA 'Review vol. 15 (1954) pages 469-484, can be used with similar results.) An image is formed on each sample, as indicated in Table 5. Another sample of each coating is tested to determine its electrical speed and maximum sensitivity peak. This is accomplished by giving each element a positive or negative charge (as indicated in Table 5) with a corona source until the surface potential, as measured by an electrometer probe, reaches 600 volts. It is then exposed to light from a 3000 K. tungsten source of 20-foot candle illuminance at the exposure surface. The exposure is made through a stepped density gray scale. The exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential, V0, to some lower potential, V, whose exact value depends on the actual amount of exposure in meter-candle-seconds received by the area. The results of these measurements are plotted on a graph of surface potential V vs. log exposure for each step. The actual speed of each element is expressed in terms of the reciprocal of the exposure required to reduce the surface potential by volts. Hence, the speeds given in Table 1 are the numerical expression of 10 divided by the exposure in metercandle-seconds required to reduce the 600 volts charged surface potential by 100 volts. The results are shown in Table 5 below.

Referring to the above Table 5, it will be seen that the control example containing the same photoconductor but no dye shows speeds of only 8 and 7 for the positively and negatively charged surfaces, respectively, whereas the corresponding values for the dye of Example 1 are 280 and 2.00 for the positively and negatively charged surfaces, respectively, with maximum sensitivity peak at 565 nm., thus indicating a speed increase over that of the control by a. factor of about 35 for the positively charged and about 25 for the negatively charged surfaces. Also of great significance is the extension of the absolute sensitivity up to about the orange region of the spectrum. Even with the least speed shown for the compositions and elements of the invention as illustrated by Example 2A improvement in speed is impressive in comparison with that of the control by a factor of about 3 for the positive charged surface with maximum sensitivity at 545 nm.

Similar results to those shown in above Table 5 are obtained, when, for example, the organic photoconductor 4,4 bis(diethylamino) 2,2 dimethyltriphenylmethane is replaced with 0.15 g. of triphenylamine, or 1,3,5-triphenyl-Z-pyrazoline, or 2,3,4,5-tetraphenylpyrrole, or 4,4- bis-diethylaminobenzophenone or when other dyes of the invention embraced by Formula I above are used. These results show that the dyes of this invention elfectively spectrally sensitize a wide variety of organic photoconductors. The dyes of this invention are not in themselves photoconductive. Also, it should be noted that the above mentioned photoconductors when used alone have very low photoconductive speed to visible light. However, as shown by the tests, the combination of the dyes of the invention with the photoconductors of the invention provide compositions and elements of outstanding speed and excellent quality of image.

This invention is highly unexpected because dyes previously suggested for spectral sensitizers impart weak spectral sensitization to organic photoconductors. Typical dyes proposed by the prior art as spectral sensitizers,

'19 which produce weak spectral sensitization in these systems, are shown in Table C below.

In contrast, as indicated previously, the dyes of this invention are inoperable as spectral sensitizers for conventional negative type photographic silver halide emulsions because they strongly desensitize such emulsions.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be efiected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. A composition of matter comprising an organic photoconductor sensitized with a dye selected from the group consisting of a cyanine dye and a styryl dye, said dye containing a moiety selected from the group consisting of a 1,3,2-dioxaborinium salt moiety, a 1,3,2-oxazaborinium salt moiety and a 1,3,2-diazoborinium salt moiety.

2. A composition comprising an organic photoconductor spectrally sensitized with a methine dye represented by one of the following formulas:

wherein d, g, m and it each represents a positive integer of from 1 to 2; L represents a methine linkage; R and R each represents an alkyl group; R represents a member selected from the class consisting of an aryl group, a 2-thieny1 group and, taken together with R the atoms required to complete a benzo or naphtho group; R taken alone represents a hydrogen atom; R represents a member selected from the group consisting of a dialkylamino group, an alkoxy group, a styryl group, and a nitro group; R represents an aryl group; R represents an aryl group; R and R each represents an alkyl group; X represents an acid anion; D and D each represents a member selected from the group consisting of an oxygen atom and an imino group; D being an imino group when D is an imino group; and Z represents the non-metallic atoms necessary to complete a nitrogen containing heterocyclic nucleus of the type used in cyanine dyes containing from 5 to 6 atoms in the heterocyclic ring. 3. The composition of claim 1 wherein said dye is selected from the group consisting of 2-fluoro-4 (4-methoxystyryl)benzo[e]-1,3,2-dioxaborinium fluoride; 2-fluoro-4- (4-nitrostyry1)benzo [e] -1,3,2-dioxaborinium fluoride;

2-fluoro-4- [2- 1-methyl-2-phenyl-3 -indolyl) vinyl] benzo[e]-1,3,2-di0xaborinium fluoride;

4- [2- (3 ,5 -dimethyl- 1-phenyl-4-pyrazolyl) -vinyl1-2-fluoroben-z0[e]-l,3,2-dioxaborinium fluoride;

4- [4dimethylaminophenyl -1 ,3 -butadienyl] -2-fluorobenzo[e]-1,3,2-dioxaborinium fluoride;

4-fluoro-4- (4-styryl-styryl) -benzo [e] -1,3,2-dioxaborinium fluoride;

4- (4-dimethylaminostyryl) -2-fluoro-naphtho[ 1,2-d]

1,3,2-dioxaborinium fluoride;

4- [4- (4-dimethylaminophenyl) -1,3-butadienyl] -2-fluoronaphth0[1,2-d]-1,3,2-dioxab0riniurn fluoride;

2,2'-difluoro-4,4'-benzo [e] -1,3 ,2-dioxaborino -carbocyanine fluoride;

2,2'-difluoro-4,4'-naphtho 1,2-d] -1,3 ,Z-dioxaborino carbocyanine fluoride;

2,2'-difluoro-4,4'-naphtho 1,2-d] -1,3 ,2-dioxaborinodicarbocyanine fluoride;

2,2'-difluoro-4,4-(benzo[e]-1,3,2-dioxaborino)-dicarbocyanine fluoride;

3 -ethyl-2-fluoro-4- 1 ,3 ,Z-benzo [e] dioxaborino -2'- thiacyanine iodide;

3 '-ethyl-2-fluoro-4-naphtho[1,2-d]-1,3,2-dioxaborino- 2-oxacarbocyanine iodide;

3 -ethyl-2-fluoro-4-naphtho 1,2-d] -1,3 ,Z-dioxaborino- 2'-thiacarbocyanine iodide;

1-ethyl-2-fluoro-4-naphtho[1,2-d]-1,3,2-dioxaborino- 2'-carbocyanine iodide;

4-(4-dimethylaminostyryl) -2-fluoro-6-phenyl-1,3 ,2-

dioxaborinium fluoride;

2-fluoro-4- [2- 1 -methyl-2-phenyl-3 -indolyl) vinyl] 6- (4-nitrophenyl) -1,3,2-dioxaborinium fluoride and 2,2'-difluoro-6,6'-di- (Z-thienyl) -4,4'-( 1,3 ,2-dioxaborino) carbocyanine fluoride.

4. An electrophotographic element comprising a conductive support having thereon a layer comprising an organic photoconductor in an insulating binder, said organic photoconductor being spectrally sensitized with a dye selected from the group consisting of cyanine dye and a styryl dye, said dye containing a moiety selected from the group consisting of a 1,3,2-dioxaborinium salt moiety, a 1,3,2-oxazaborinium salt moiety and a 1,3,2- diazaborinium salt moiety.

'5. An electrophotographic element in accordance with claim 4 wherein said dye is represented by one of the following formulas:

wherein d, g, m and n each represents a positive integer of from 1 to 2; L represents a methine linkage; R and R each represents an alkyl group; R represents a member selected from the class consisting of an aryl group, a 2- thienyl group and, taken together [with R the atoms required to complete a benzo or naphtho group; R taken alone represents a hydrogen atom; R represents a member selected from the group consisting of a dialkylamino group, an alkoxy group, a styryl group, and a nitro group; R represents an aryl group; R represents an aryl group; R and R each represents an alkyl group; X represents an acid anion; D and D each represents a member selected from the group consisting of an oxygen atom and an imino group; D being an imino group when D is an imino group; and Z represents the non-metallic atoms necessary to complete a nitrogen containing heterocyclic nucleus of the type used in cyanine dyes containing from 5 to 6 atoms in the heterocyclic ring.

References Cited UNITED STATES PATENTS 3,127,266 3/ 1964 Sus et a1. 961

GEORG'E F. LESMES, Primary Examiner 5 JOHN C. COOPER H'I, Assistant Examiner U.S. Cl. X.'R. 

